Butterfly the chicken breasts by cutting in half horizontally (but not all the way through) and opening up like a book. Lay clingfilm over the top and gently bash until they are a similar thickness all over.
Heat a non-stick frying pan to hot then lightly oil and season the chicken and add to the pan. Sear for 2-3 minutes on each side until golden and cooked through.
Lift onto a baking tray then spread the pesto over each breast. Add a couple of slices of pepper and top with the mozzarella. Season.
Slide under a hot grill and cook until the cheese is melted and bubbling. Finish with some fresh basil and serve with salad.